Storm Prediction Center Mesoscale Discussion 1844

   Mesoscale Discussion 1844
   NWS Storm Prediction Center Norman OK
   1206 PM CDT Tue Aug 06 2024

   Areas affected...Portions of eastern Pennsylvania...New Jersey...far
   eastern Maryland...northern Delaware

   Concerning...Severe potential...Severe Thunderstorm Watch likely 

   Valid 061706Z - 061830Z

   Probability of Watch Issuance...80 percent

   SUMMARY...The severe threat should increase through the afternoon,
   with multiple rounds of strong to severe thunderstorms expected.
   Damaging gusts are the main threat, though a couple instances of
   large hail or a tornado are also possible. A Severe Thunderstorm
   Watch issuance will eventually be needed.

   DISCUSSION...Multiple semi-discrete, robust updrafts (including
   supercells) have become established over western PA and are poised
   to track eastward through the afternoon. However, before these
   storms cross the Appalachians, at least scattered thunderstorms are
   expected to develop east of the Appalachians amid a destabilizing
   airmass. Visible satellite shows a rapidly expanding CU field, with
   MRMS mosaic radar data showing convective initiation potentially
   already underway. To the lee of the Appalachians, surface
   temperatures are already reaching 90 F amid 70+ F dewpoints,
   supporting 8 C/km boundary-layer lapse rates (per 16Z mesoanalysis).
   Though deep-layer shear should remain modest through at least early
   to mid afternoon (i.e. around 30 kts effective bulk shear), the
   steepening low-level lapse rates will support a damaging gust
   threat.

   Later this afternoon, as the stronger storms to the west approach
   the region, an instance or two of large hail and maybe even a
   tornado could occur as these storms traverse a baroclinic boundary,
   where low-level shear may be locally maximized. A Severe
   Thunderstorm Watch will be needed soon to address the impending
   severe threat.

   ..Squitieri/Hart.. 08/06/2024

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...OKX...PHI...BGM...CTP...LWX...

   LAT...LON   41547634 41337471 41107410 40487393 39777413 39157450
               39087501 39117540 39457603 40057578 40817586 41547634